Where do we find a site with all the libretti we are missing these days..

[mc ukrneal]

Brilliant have a few at their opera website as well:
http://www.brilliantoperacollection.com/

[Superhorn]

  I don't know if the superb Boulez/Concertgebouw/DG recording of Moses& Aron is still available, but I bought it several years ago, and it has the libretto and translation,ditto the Solti/Chicago Decca recording.  Check arkivmusic.com for these.
  They're the best website to look for hard to find recordings.